This invention relates, in general, to amplifier circuits, and more particularly, to amplifiers for amplifying a differential voltage and providing a single-ended voltage.
An increasing number of electronic circuits are powered by batteries. Cellular telephones, personal computers, and stereo systems are just a few of the devices that are made portable by the use of batteries. Battery technology is driven to provide batteries of increased power while reducing battery size and weight. Rechargeable batteries such as nickel cadmium, nickel-metal hydride, or lithium are extremely popular on devices that are frequently used.
Battery chargers must accurately control the voltage and current provided to a charging battery. Overcharging a battery can damage the battery or reduce the battery life. A precision amplifier is required in a battery charger circuit to monitor current provided to a charging battery. In general, a resistor is placed between a battery charger circuit and the battery for monitoring charging current. The voltage across the resistor corresponds to the charging current being provided to the battery. The precision amplifier amplifies the voltage across the resistor and provides a feedback signal corresponding to the charging current. The battery charger circuit is continuously adjusted to prevent overcharging based on the charging time period, magnitude of the charging current, and the battery voltage.
It would be of great benefit if an amplifier could be provided that accurately senses a differential voltage and is easily integrated on a semiconductor wafer process.